Comparison of stratospheric temperatures from several lidars, using National Meteorological Center and microwave limb sounder data as transfer references

Abstract

Stratospheric temperatures derived from five different lidars are compared. Although the lidars are in five separate geographic locations, the evaluation is accomplished by comparing each of the sets of lidar data taken over the course of a year (1991–1992) with temperatures interpolated to each location from daily global temperature analyses from the National Meteorological Center (NMC). Average differences between the lidars and NMC temperatures vary for the different lidars by up to 6.7 K. Part of this large average temperature difference is shown to be due to the real temperature variation throughout the day, and the different times of observation of the NMC data and each of the lidar systems. Microwave limb sounder (MLS) data from the upper atmosphere research satellite are used to model the diurnal and semidiurnal variations in temperature for each lidar location, for each season. After adjusting for the temperature changes caused by variations in observation time, average temperature differences are reduced among four of the five lidars, compared with the NMC temperatures, but still vary by as much as 3.9 K at stratospheric altitudes between 30 and 45 km. Results of direct comparisons at two permanent lidar sites with a mobile lidar show that sometimes agreement within 1 to 2 K is achieved, but for other cases, larger average differences are seen. Since the precision of lidar temperatures has been estimated to be better than 1 K, further research is needed to reconcile this small expected error with the larger average differences deduced here using measurements made under operational conditions.